Functional Impact Analysis for Complex Critical Infrastructure Systems

Abstract

The well-being of the population depends to a large extent on services of critical infrastructures (CIs). It is a wellknown fact that the dependencies between CIs lead to even greater impacts on society in the case of malfunctions. To assess these impacts, understand and mitigate them, it is essential to determine and possibly quantify the dependencies. The approach described here consists of three steps. First, the disruptive event for which the impacts should be analyzed is defined (e.g. a blackout). In a second step, the infrastructure system is modeled. For this purpose, the system is divided into its entities according to common CI definition. Then, the possible service levels of each entity are assessed and quantified, such as standard operation mode, emergency operation mode or breakdown. Logically linked requirements for reaching those levels are defined, either autonomously or as an external dependency (e.g. a power generator), forming a system of dependent services. In a third step, impacts of events are analyzed by degrading selected services and calculating the effects on other services according to the logically linked requirements. Uncertainties can be described by specifying probabilities for service levels. The development over time can be examined by evaluating the impacts of sequential time intervals, e.g. for a regional blackout, where more CIs will face difficulties over time.